This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 28 586.4, filed on Jun. 14, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a shock absorber for taking up the impact shock of a moving component, and then slowing down and stopping the component. The shock absorber includes a housing, a piston axially slidably arranged in the housing, a piston rod connected to the piston and extending outwardly through a seal at an end of the housing, and a contact or stop element connected to the end of the piston rod opposite the piston. A moving load component, which is to be slowed down and stopped, strikes against the stop element, whereupon the piston is slidingly moved while displacing a hydraulic fluid through a throttling arrangement to dissipate the kinetic energy. A mechanical support element limits the maximum stroke of the piston.
The above described general type of shock absorber is conventionally known for slowing down and stopping various moving load components, such as moving machine parts, items being transported on a conveyor belt or the like, and any other component that must be slowed down and stopped in a gentle damping manner.
A conventionally known shock absorber of this type may further include an adjusting mechanism including an adjusting ring protruding from an end of the shock absorber. This mechanism allows the damping constant or coefficient of the shock absorber to be adjusted by rotating the adjusting ring. For this purpose, the adjusting ring is securely fixed in a torque transmitting manner to a rotatable adjusting sleeve. A so-called pressure sleeve is located within the adjusting sleeve, and in turn, the piston is axially slidably arranged in the inner space within the pressure sleeve. The pressure sleeve has throttle holes therein, and the effective open cross-sectional area of these throttle holes is variable by rotating the adjusting sleeve while the pressure sleeve remains stationary i.e. does not rotate. The rotation of the adjusting sleeve is achieved by rotating the adjusting ring provided at an end of the housing.
In the conventionally known shock absorber, the adjusting ring that protrudes out of an end of the housing directly serves as a mechanical support element that limits the maximum travel or stroke of the piston. Namely, the stop element and/or the load to be slowed down and stopped will strike against and be positively stopped by the adjusting ring, after the stop element and the connected piston have traveled through the maximum allowable stroke.
A disadvantage of such a conventional arrangement is that very great forces will be introduced into the support element, i.e. the adjusting ring in the conventional shock absorber, when a large load has contacted and pushed against the stop element and thereby pushed the piston through its maximum allowable stroke. As a result, the adjusting ring is very heavily loaded, for example even to the extent that plastic deformations arise in the adjusting ring or in various force transmitting or bearing components within the shock absorber housing. As a result, the adjustability of the shock absorber is negatively influenced or even made impossible.
In view of the above it is an object of the invention to provide a shock absorber having an adjusting ring arranged at an end of the shock absorber housing, which is further developed and improved in such a manner so that the moving load component or the stop element will not bear directly against and apply a damaging load to the adjusting ring when the piston has been moved to the extent of the maximum allowable piston stroke. It is a further object of the invention to provide a compact shock absorber construction which fully-protects the adjusting ring by preventing any stop loads from being applied to the adjusting ring. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a shock absorber including a housing, a piston axially slidably arranged in the housing, a piston rod connected to the piston and extending through a seal at one end of the housing, and a contact or stop element that is arranged on an end of the piston rod opposite the piston and that is adapted to be contacted by a moving load component that is to be slowed down and stopped. The moving load component bearing against the contact or stop element causes the piston to be axially moved in the housing and thereby to displace a hydraulic fluid through a throttling arrangement, so as to dissipate the kinetic energy of the moving load component.
Further according to the invention, an adjusting ring, with which the damping coefficient of the shock absorber can be adjusted, is arranged surrounding the piston rod at the first end of the shock absorber housing through which the piston rod protrudes. Moreover, a support element is provided by a rigid part of the housing itself, preferably at the first end of the housing through which the piston rod protrudes. The support element is arranged and adapted to cooperate with the contact or stop element, so that the stop element will bear directly against the support element without bearing against the adjusting ring, when the piston has traveled to the end of the maximum allowable piston stroke. Preferably, the stop element comprises a pot-shaped or cup-shaped stop cap with a hollow cup space therein, which accommodates the adjusting ring therein when the protruding rim of the cup-shaped stop cap bears against the support element in the end position at the maximum allowable travel of the piston.
With the inventive arrangement of a shock absorber, in the case of a large moving load bearing against the stop element, the arising forces will be transmitted directly from the stop element into the support element which is a rigid part of the shock absorber housing itself, once the piston and parts connected thereto have reached the end limit of the maximum allowable travel. In this manner, there is no danger of applying a load from the stop element onto the adjusting ring, which might otherwise damage the rotatable adjusting ring. The rigid positive stop and contact of the stop element against the rigid support element of the housing itself enables an especially large force transmission and force introduction directly from the stop element into the robust housing of the shock absorber, without causing any possible damage of the components of the shock absorber or any interference or interruption of the proper functioning thereof.
Even though the adjusting ring protrudes axially from the first end of the shock absorber housing, and is thus the furthest outwardly protruding part of the shock absorber housing or body, the adjusting ring is completely protected and will not have any forces introduced thereto when the stop cap bears against the support surface at this end of the housing. Thus, the invention provides the advantages of a very simple adjustability of the damping characteristic of the shock absorber by simply turning the adjusting ring (when it is exposed, i.e. uncovered by the stop cap being moved to a position away from the end limit position in which the stop cap encloses the adjusting ring). In combination therewith, the invention provides the advantages of a positive mechanical stop to limit the travel of the piston and of the stop element connected thereto, with a positive mechanical load introduction from the stop cap directly into the robust housing of the shock absorber.
Preferably, the cup-shaped stop cap includes an outer cylindrical A sleeve terminating at an annular or ring-shaped end face of the cap, which contacts against a corresponding annular or ring-shaped end face of the housing part forming the stop element. This arrangement is provided radially outwardly and circumferentially around the adjusting ring. In this manner, the adjusting ring is completely protected against any loads being applied thereto, and instead the force introduction is carried out through a rather large surface area distributed about the circumference of the cylindrical shock absorber housing. Thereby, the surface pressure or loading at any given area is maintained uniformly at a correspondingly low level. Preferably in this context, the outer diameter of the stop cap corresponds to the outer diameter of the cylindrical housing in the area of an end ring of the housing that faces toward and contacts the rim of the stop cap. This provides a flush exterior transition between the stop cap and the shock absorber housing when the piston has been depressed inwardly to the end limit of its maximum travel.
According to a further embodiment detail of the invention, a pressure reservoir chamber or accumulator chamber is formed or defined in an annular chamber on the backside of the piston between the inner circumferential surface of the housing and an outer circumferential surface of a bearing sleeve or guide sleeve that guides and seals the piston rod extending through a central bore thereof. On the other hand, the outer cylindrical surface of the guide sleeve is sealingly supported on the inner circumferential surface of the housing. Thereby, simultaneously, the pressure reservoir or accumulator chamber is bounded at an end face facing toward the exterior of the shock absorber. In this context, the inner diameter of the stop cap preferably corresponds to the inner diameter of the housing in the area of the accumulator chamber.
A further detail of the invention provides that the stop cap is preferably screwed or bolted onto the free end of the piston rod, and that a return spring is arranged coaxially around the piston rod, to be braced between the interior of the stop cap and an end surface of the housing, for example coaxially radially inwardly relative to the adjusting ring. This return spring bears against the stop cap to press the stop cap outwardly away from the shock absorber housing, and thereby to return the piston rod and the piston from the end limit stop position (or retracted position) to the initial load receiving and damping position (or extended position). In this context, the compressed return spring is preferably fully accommodated and enclosed within the hollow inner cup space of the stop cap in the end limit stop position. Preferably, the outer diameter of the spiral or helical return spring is smaller than the inner diameter of the adjusting ring, so as to fit radially within the adjusting ring as mentioned above.
Further according to the invention, the adjusting ring is secured to a bearing sleeve in a rotation-fixed manner, i.e. so that the adjusting ring cannot rotate relative to the bearing sleeve, but rather the adjusting ring and the bearing sleeve will turn or rotate in common with each other. A turning or rotation of the bearing sleeve by correspondingly turning the adjusting ring serves to selectively cover or uncover the effective cross-sectional flow passage area of at least one throttle opening provided in a pressure pipe, so as to adjust the damping coefficient of the shock absorber.